So he organized the workforce according to the requirements of his equipment and design, and said, “Bring me blocks of iron” (18:96)—meaning, collect for me every scrap of iron you can find, large or small, leave nothing behind, and heap it in the gap between the two barriers. They obeyed until the iron rose in massive mounds that matched the height of the mountains—hence the words, “until, when he had leveled it with the two mountain-sides.”
He then said, “Blow!”—that is, fan the fire—“until, when he had made it a blazing mass, he said, ‘Bring me molten brass that I may pour over it’” (18:96). He ordered that copper be smelted in the furnaces and poured so that it flowed among the iron blocks, binding them together until the whole became an awe-inspiring rampart fused to the two natural barriers. The aim of restraining Gog and Magog was thus achieved, and for this reason Allah says, “Thus they were unable to climb over it, nor were they able to pierce it. (18:97) He said, ‘This is a mercy from my Lord’”—that is, my Lord, who enabled me to accomplish this magnificent work and leave this noble legacy, has shown you mercy by shielding you from the harm of Gog and Magog through a means far beyond your own power.
“But when my Lord’s promise arrives, He will level it” (18:98)—in other words, this construction and the barrier between you and Gog and Magog are only temporary. When the appointed time comes, Allah will grant humankind such power, capability, industries, and astonishing inventions that Gog and Magog will be able to trample your lands, O neighbours of the rampart, and indeed to overrun both the eastern and western extremities of the earth. As He says: “until, when Gog and Magog are let loose and they swarm down from every rise” (21:96)—that is, from every elevated place, whether over such barriers, across the seas, or through the very air above.
The term “they swarm” means they will surge forward swiftly, heedless and unchecked, with no barrier to restrain them. The phrase “from every rise” embraces all locations and regions—easy and difficult, low-lying and high. Allah singled out the heights only because if they can descend from the lofty places, then the plains and lowlands are, a fortiori, even more accessible.